The prior art has provided several slow release fertilizers which work by occluding soluble fertilizer materials within agglomerates bound together by water insoluble binders. For example nitrogen, phosphorus, potassium and micronutrients may be bound together with ureaformaldehyde resins, or as in the case of U.S. Pat. No. 3,925,053 calcium sulfate hemihydrate may be used as a binder.
U.S. Pat. No. 3,647,416 discloses that bonded fertilizers may be produced in the form of a briquette using ureaformaldehyde resin as the binder. U.S. Pat. No. 3,024,098 also discloses a ureaformaldehyde based fertilizer which is prepared by compressing into agglomerates to provide briquettes or spikes with high resistances to crushing.
Compressed briquettes have also been prepared with improved nitrogen release when isobutylidiene diurea was the main source of nitrogen.
There has been less information in the prior art regarding controlled release of pesticides than of plant nutrients. There has been some success reported in controlling pesticide release rates when granular pesticides were coated or encapsulated with water insoluble plastics such as polyvinylchloride as in U.S. Pat. No. 3,062,637.
In U.S. Pat. No. 5,174,804 a fertilizer/pesticide composition was disclosed which included a fertilizer and a pesticide admixed with a binder to form a briquette in which the fertilizer occludes the pesticide, with the briquette essentially free of water soluble materials. This briquette when placed in the soil releases nutrients and pesticides into the soil over an extended period of time.
Although U.S. Pat. No. 5,174,804 advanced the art of controlled release plant nutrients and pesticides, it did not provide a method for separate control of the release of the pesticides and the plant nutrients. It also does not provide for wide variations in the amounts of pesticide or plant nutrient materials in a briquette product.